Transistor voltage regulating system for generators having main and reverse field windings



L. J. RAVER ET AL 3,512,075

May 12, 1970 TRANSISTOR VOLTAGE REGULATING SYSTEM FOR GENERATO HAVING MAIN AND REVERSE FIELD WINDINGS 2 Sheets-Sheet 1 Filed Sept. 11, 1968 /////fl J1? 4 0' NOTCH TOOTH NOTCH 6 MAIN 8.9

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RADIAL AlRGAP FLUX I GEglI-ZRATOR OF ROTOR UTPUT JZ yf REGULATlNG/ NT RS SYSTEM [01113 [Raver 5 BY @Maziz" L: Ka/zqva Ma 4M ATTORNEY May 12, 1970 1.. J. RAVER ET AL 3,512,075

TRANSISTOR VOLTAGE REGULATING SYSTEM FOR GENERATORS HAVING MAIN AND REVERSE FIELD WINDINGS Filed Sept. 11, 1968 2 Sheets-Shet 2 do; in; W!

INVENTORS [011119 I Ra V61 (5 BY fizram L Kmopa 4% MM ATTORNEY United States Patent US. Cl. 322--28 4 Claims ABSTRACT OF THE DISCLOSURE In a preferred embodiment, a voltage regulating system is provided for a generator having an output winding, main and reverse field windings and a permanent magnet field provided by one or more permanent magnets. The regulating system is capable of maintaining the output voltage of the generator substantially constant and includes first and second output transistors connected in series respectively with the main and reverse field windings of the generator and across the output winding of the generator. A voltage sensing circuit senses the output voltage of the generator and biases both the first output transistor and a driver transistor connected to the second output transistor alternately conductive and nonconductive as a function of generator output voltage. The system is operative to bias the first output transistor conductive when the second output transistor is biased nonconductive and vice versa. The reverse field winding when energized by the conduction of the second output transistor develops a flux which opposes the effect of the magnetic field provided by generator permanent magnets.

This invention relates to voltage regulators for generators and more particularly to a voltage regulator which is capable of regulating the output voltage of a generator which has a permanent magnet field and main and reverse field windings.

The output voltage of a generator which has a field winding can be controlled by regulating the amount of field current supplied to the field winding as is well known to those skilled in the art. The present invention is concerned with a voltage regulator for a generator that includes a permanent magnet field which aids the generator main field to increase the maximum available generator output current. One generator of this type is disclosed in copending United States patent application of Robert W. Campbell, S.N. 381,127 now Pat. No. 3,392,294, filed on July 8, 1964, and assigned to the assignee of this invention.

The generator of the above-mentioned copending application can be regulated to some extent by controlling the amount of current supplied to a main field winding. It is apparent, however, that even if the excitation current for the main field winding is reduced to substantially zero the magnetic field produced by the residual induction of the permanent magnets will still cause a voltage to be generated in the output winding of the generator. It has been found that this permanent magnet field is sufficient to cause a voltage to be generated that is higher than the desired regulated value when the generator is driven at high speed and at the same time is operating under a light electrical load.

The magnetic field provided by the permanent magnets of the generator can be opposed by providing a reverse field winding for the generator. The magnetic flux of the reverse field winding opposes the effect of flux developed by the permanent magnets to therefore maintain a desired generator output voltage. When the generator is utilized in a vehicle electrical system, including a battery 3,512,075 Patented May 12, 1970 charging circuit, voltage regulation is especially important to avoid shortened battery life that might otherwise be caused by either low or excessive charging voltages.

Although the regulating system of this invention is designed specifically to regulate the out-put voltage of a generator which includes permanent magnets it can also have utility in generating systems where residual induction is developed by the residual magnetism of the magnetic circuit of the generator. An excessive voltage can be generated in this type of system and the flux developed by a reverse field winding can be utilized to oppose the residual magnetic field. It will, of course, be appreciated by those skilled in the art that generators with magnetic circuits having high retentivity provide some degree of residual magnetism, and this type of magnetic circuit is utilized to provide a generator which will initially build up voltage without some initial excitation of the field winding of the generator.

In the present invention a regulating system for generators having main and reverse field windings is provided which is capable of precisely regulating the generator output voltage while operating with varying loads and speeds. The reverse field winding is energized to oppose the eifect of the permanent magnet flux and the main field is deenergized when the output voltage of the generator exceeds a desired regulated value.

Accordingly, it is an object of this invention to provide a generator voltage regulating system including a reverse field winding control circuit that is operative to control the amount of current supplied to the reverse field winding as a function of output voltage of the generator.

A further object of this invention is to provide a variable speed alternating current generator with a transistor voltage regulating system that energizes the main field winding when the generator output voltage drops below a desired regulated value and energizes a reverse field winding in response to the same control which deenergizes the main field winding.

A further object of this invention is to provide a generator voltage regulating system for a generator having a main field winding, a reverse field winding and a magnetized core portion producing flux due to the residual induction of permanent magnets or residual magnetism. The regulating system includes a control circuit which energizes the reverse field to neutralize the effect of the magnetized portion and simultaneously deenergizes the main field winding when the output voltage of the generator exceeds a desired regulated value.

A still further object of this invention is to provide a variable speed alternating current generator adapted for use in land or marine vehicles including heavy duty electrical systems with a transistor voltage regulating system including one output transistor responsive to the genera tor output voltage and periodically switching voltage from a generator load circuit output to control the current supplied to a main field winding. A second output transistor periodically switches voltage applied from an auxiliary generator output to control current of a reverse field winding. The second output transistor is controlled by a driver transistor that is responsive to the same voltage developed to control the first output transistor so that the transistors are alternately biased conductive and nonconductive.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIG. 1 is a perspective view, partially in section, of a generator having main and reverse field windings and permanent magnets which is regulated by the voltage regulating system of this invention.

FIG. 2 is a fragmentary perspective view illustrating the operation of the generator shown in FIG. 1.

FIG. 3 illustrates graphs of flux distribution across the air gap of the generator shown in FIG. 2.

FIG. 4 is a schematic circuit diagram of a generator voltage regulating system made in accordance with the present invention.

Referring now to FIG. 1 wherein reference numeral generally designates an alternating current generator which is regulated by the voltage regulator of this invention. The generator 10 is of the brushless homopolar inductor type described and claimed in the aforementioned application S.N. 381,127, filed July 8, 1964.

The generator provides a rugged and compact machine intended for use, in one working embodiment, as the generator power source for electrical systems of large land vehicles or boats having inboard engines. An increased generator power output is provided by incorporating a permanent magnet field in aiding relationship to the flux distribution produced by a main field flux. Since the permanent magnetic field is continuous, an opposing flux field is required to cancel the voltage producing effect of the permanent magnetic flux so that the generator output can be regulated as described more fully hereinbelo w. Alternating current generator 10 is described by way of example and not limitation as one type of generator intended to be controlled by the control arrangement of this invention.

The alternating current generator 10 includes a frame portion 12 supporting a stator core formed by two aligned stacks of laminations 14 and 15. The stator laminations are made of a magnetic material and each include stator tooth portions 16 which form stator slots indicated by numeral 18. The slots 18 of each stator stack receive conductors of a generator output winding designated 22. The winding 22 is only partially illustrated in some of the slots 18 as an example of the coil conductors of winding 22 which are wound in a three phase Y connected configuration in a conventional manner.

The space between the stacks of stator laminations 14 and contains a main field winding designated 24 and a reverse field Winding designated 26. The generator windings 22, 24 and 26 terminate in connections, not shown suitable for connection to a circuit including the control arrangement of this invention described hereinbelow.

The generator has a rotor generally indicated by num-' eral 30 which is mounted within the stator core laminations and includes a rotor shaft 32 that is rotatably supported by hearing members, not shown. The rotor 30 is adapted to be driven by a vehicle internal combustion engine, also not shown. A first stack of rotor laminations designated 34 and shown at the left end of rotor 30 and a second stack of rotor laminations designated 36 and shown at the right end of rotor 30 are both made of magnetic material and are securely mounted on shaft 32. Rotor stacks 34 and 36 are separated by a rotor core portion 38 which is formed of magnetic material. The core portion 38 forms a magnetic circuit path between the rotor stacks 34 and 36.

Each of the rotor stacks comprises six tooth portions respectively designated 42 and 44. The space between adjacent rotor teeth of each rotor stack forms notches designated 46 and 48, respectively, on each rotor stack. The axis of each tooth of one rotor stack is aligned with the center of a notch of the other rotor stack. Selected notches receive permanent magnets designated 52 and 54, respectively, carried by the rotor stacks 34 and 36. Accordingly, the axes of permanent magnets '52 and 54 are respectively aligned with the tooth axes of the teeth 44 and 42.

The four permanent magnets designated 52, illustrated on the first rotor stack 34, have a common radial polarity. Also, the four permanent magnets designated 54 on the second rotor stack 36 have a common and mutually opposite radial polarity to that of permanent magnets 52 of the first rotor stack. For example, the outer tip of each permanent magnet 52 is a south pole while the outer tip of each permanent magnet 54 is a north pole.

Each of the permanent magnets 52 and 54 is formed by a bar of permanently magnetized material having end grooves indicated by numeral 56. Each permanent magnet is attached to a rotor stack by means of a cap 58 and screws 60 fastened to the rotor stack. With cap 58 and screws 60 in place, each permanent magnet is accordingly clamped between a cap 58 and the bottom of the respective rotor notches 46 and 48.

Although two opposite notches of each stack are shown vacant, all the notches can be provided with permanent magnets to further increase the output in accordance with the operation of this generator. The four vacant notches illustrated in the embodiment of FIG. 1 improve air circulation when increased generator cooling is required.

The output of the generator shown in FIG. 1 was compared with the output of a similar generator having permanent magnets 52 and 54 removed. The maximum output current capability was increased an average of thirty percent above the output produced without the magnets throughout the operating speed range of the generator. However, at some low load conditions the permanent magnets continued increasing the generator power output with the main field deenergized so that an opposing or reverse field flux is required to provide proper voltage regulation.

The operation of the generator 10 illustrated in FIG. 1 is described with reference to FIGS. 2 and 3. FIG. 2 shows a fragmentary view of a rotor 30 having stacks designated 34' and 36, main and reverse field windings 24 and 26 and a single turn coil designated 62 which represents a coil of the output winding 22. The coil 62 is shown in an exploded position having a coil axis 64. The coil is illustrated wound about a single elongated stator tooth 18; although in the generator of FIG. 1 a coil encompasses three teeth so that the Width of the coil sides is equal to the distance between the centers of a notch and a rotor tooth.

It is to be understood that the coil 62 has a voltage induced therein and this voltage is indicated at 66 and is applied to the voltage regulating system of the present invention represented by the block designated 70. Regulating system 70 controls the current supplied to the main field winding 24 and the reverse field winding 26 in response to the generator output 66 as described further hereinbelow.

To explain the effect of the permanent magnets, the first rotor stack 34 is illustrated with two permanent magnets 52 in the notches 46 adjacent rotor tooth 42 having the radial polarity indicated. Stack 34' rotates beneath the forward end 62a of coil 62. The second rotor stack 36 is illustrated including a permanent magnet 54 between the two rotor teeth 44. Accordingly, the stack 36' rotates beneath the rear portion 62b of coil 62. The magnet 54 is aligned along the common axis 72 with tooth 42 and has the indicated radial polarity opposite that of magnets 52. The description of operation of FIG. 2 correspondingly applies to the generator of FIG. 1 by considering a permanent magnet placed in each rotor notch so that twelve rather than eight permanent magnets would be required. As noted above, increasing the number of magnets will correspondingly increase the generator output.

The main field winding 24 produces a flux represented by arrows 74 and the reverse field winding 26 produces a flux represented by arrows 76 in an opposite direction. The magnetic fluxes 74 and 76 flow radially through the teeth of each rotor stack such that each flux is opposite to the other but each has a constant direction through each tooth of a given rotor stack. This generator is characterized as being a homopolar flux machine because fiux is produced in a common direction relative to the ends of the generator.

The radial magnetic flux across the air gap between the rotor and stator is referred to as the air gap flux which is represented by the arrows at the tips of the rotor teeth and permanent magnets. The arrows 74 and 76 indicate the direction of the fluxes resulting from the corresponding main and reverse magnetic fields producing them. Accordingly, the flux of teeth 42 and 44 produced by the main field flux 74 is outward at tooth 42, inward at tooth 44 and vice versa for reverse field flux 76.

The air gap fluxes produced by permanent magnets 52 and 54 are indicated respectively by arrows 78 and 80. The flux 78 of permanent magnets 52 is radially inward and arrows 80 indicate that air gap flux produced by permanent magnet 54 is radially outward.

FIG. 3 illustrates the distribution of radial air gap flux b around the periphery of the illustrated fragmentary portion of the first rotor stack 34' which is produced by the fluxes 74, 76 and 78 shown in FIG. 2. The line 84 of the upper graph indicates the difference in flux distribution between a rotor tooth 42 and a notch containing a permanent magnet 52 with the main field winding 24 producing flux 74. It is assumed in this graph that the reverse field flux 76 is not produced since the reverse field winding 26 is deenergized. The direction of flux across a notch having a permanent magnet 52 is opposite to the direction of flux of an adjacent tooth 42 as indicated by the directional arrows 74 and 78.

The dashed line portion 86 of FIG. 3 indicates the flux distribution that is provided through a notch portion without a permanent magnet. The line 84 across a notch illustrates that there is a greater change in flux from that across a tooth with the use of permanent magnets. Although the flux produced by the permanent magnets of each rotor stack is in an opposite radial direction from the flux produced by the main field winding 24, the effect of the permanent magnet fluxes is to increase the electromotive force generated in coil 62 as explained below.

It is understood that the radial air gap flux distribution of the second rotor stack 36' would be the same as illustrated in FIG. 3 except that the polarity would be reversed. This is apparent by noting the direction of corresponding flux arrows at the tips of the two rotor stacks illustrated in FIG. 2.

The bottom graph of FIG. 3 includes the line 88 illustrating the radial air gap flux of rotor 34' with the reverse field winding 26 energized and the main field flux 74 off. The flux 76 produces a substantially constant flux distribution since flux 76 is produced to substantially neutralize the effect of a change in radial flux due to the continuous flux produced by permanent magnets 52 and 54.

Without permanent magnets 52 and 54, the generator illustrated in FIG. 2 operates as a conventional homopolar generator. As is known, in the general operation of a homopolar inductor generator there is a periodic change in the magnitude of flux interlinking the output winding. The change in magnitude of the unidirectional flux at each end of the generator is produced by a rotor having alternate tooth and notch portions wherein the notches provide a high reluctance to vary the reluctance to the main field flux. Without the permanent magnets there would be a maximum of flux at the center of each tooth and a minimum flux at the center of each notch as indicated by the line 86 in the upper graph of FIG. 3.

The variable flux is rotated past a coil winding, such as coil 62, when rotor rotates to thereby produce a generated voltage or electromotive force in the generator output coils. Voltage is generated in accordance with the rate of change of magnetic flux interlinking each output coil winding. The mathematical term d/a't is commonly used to express the rate of change of magnetic flux. Since the electromotive force induced in the coil depends on the change in flux, it can be seen that the permanent magnets increase the rate of change in flux or dqS/dt because of increased difference in flux intensity 6 so that the permanent magnet fields are in an aiding relationship to the main field flux.

This can be understood by observing the rotation of the rotor of FIG. 2 in a counterclockwise direction and considering initially that the axis 72 of tooth 42 and permanent magnet 54 is approaching but not aligned with the axis 64 of coil 62. In this condition forward end 62a of coil 62 will be interlinked along its left hand portion with the inward flux 78 of the left permanent magnet 52 and the outward main field flux 74 is interlinked with the right hand portion. The right and left sides of the coil end 62a have an induced voltage produced therein in a clockwise direction around the coil 62. The opposite coil end 62b is interlinked on its right hand side with the outward flux 80 of magnet 54 and on the left hand side with the inward flux 74 of the left rotor tooth 44. The right and left hand conductors of end 62b have a voltage induced therein which is also in a clockwise direction around the coil 62.

As the axis 72 of tooth 42 and permanent magnet 54 reaches and is aligned with the axis 64 of coil 62 there is a maximum and substantially constant flux density interlinking the coil and at this instant there will be minimum voltage induced in coil 62.

As the rotor 30' continues to rotate, the axis 72 of tooth 42 and permanent magnet 54 moves beyond or to the left coil axis 64. In this relationship the voltage begins to be induced in a counterclockwise or opposite direction of that induced when axis 72 was to the right of the coil axis. This is because the flux 78 of the right permanent magnet 52 is now interlinked with the right hand portion of coil end 62a and the outward flux 74 of tooth 42 is interlinked with the left hand portion of coil 62. In like manner, the coil end 62b is interlinked on its right side with inward flux 74 of the right hand tooth 42 and on the left coil side with outward flux 80.

The induced counterclockwise voltage tends to increase and reach a maximum as the rate of change of flux between a tooth and a permanent magnet reaches a maximum. This condition corresponds to the region of the line 84 in FIG. 3 indicated at 89. As the axis 72 rotates further, the axis of right permanent magnet 52 and opposite rotor tooth 44 approaches the axis of coil 62 and the induced voltage produced in a counterclockwise direction decreases. The above-described cycle is repeated through the several stator coils by the rotation of the rotor in producing an alternating current voltage in the generator output winding 22.

When the generator regulated voltage output is reached, the regulating system 70 deenergizes the main field winding 24 so that flux 74 is no longer produced. The magnetic fields of permanent magnets 52 and 54 continue to produce the respective fluxes 78 and 8t} tending to generate an induced voltage in coil 62 if the reverse field 26 is not energized. The permanent magnet flux has a maximum intensity at the tip of each permanent magnet and a minimum intensity between adjacent magnets. At high speeds and low generator electrical loads the effect of the change in flux is increased so that the output voltage of the generator may continue above the desired regulated value. With the reverse field winding 26 energized, the reverse field flux 76 tends to substantially neutralize the change in radial flux distribution produced by the permanent magnets alone. This is seen by observing the graph of line 88 in FIG. 3. With a substantially constant flux interlinking the coil 62 the induced voltage drops and the generator output voltage is reduced to the regulated value.

The reverse field winding flux 76 produces radially inward flux at teeth 42 and outward flux at teeth 44, which is opposingly interlinked with the coil ends 62a and 62b with respect to the permanent magnet fluxes. The coil end 62a is interlinked with a substantially constant and inwardly directed flux and end 62b is interlinked with a substantially constant and outwardly directed flux. Since both ends of the coil are interlinked with substantially 7 unvarying and opposingly directed fluxes, the induced voltages cancel and there will be a negligible net voltage generated in the coil 62.

It is to be kept in mind that when the coils of generator output winding 22, as represented by the single coil 62 in FIG. 2, are supplying a load, the basic operation described above is cyclically repeated at a high rate. The main and reverse field windings 24 and 26 are alternately supplied with excitation current so that the desired generator voltage output is maintained by the regulating system 70 of this invention.

Referring now to FIG. 4, a schematic circuit diagram is shown that illustrates the generator regulating system of the present invention. The generator 10 is of the type described hereinabove and is illustrated with corresponding elements designated with like numerals to those used in FIGS. 1 and 2. The three-phase output winding 22 and main and reverse field windings 24 and 26, respectively, are illustrated connected to the voltage regulating system 70.

The direction of flux of main field winding 24 is indicated .by the arrow 74 and the oppositely directed flux of reverse field winding 26 is represented by the arrow 76. The rotor permanent magnets 52 and 54, described hereinabove, are illustrated with their respective fluxes represented by arrows 78 and 80. The direction of both arrows 78 and 80 is in the same direction as arrow 74 representing the main field flux. The common direction represents the operatively aiding relationship of the permanent magnet fields in increasing the generator voltage output as described also hereinabove.

In one embodiment of the generator voltage regulating system of this invention, the main and reverse field magnetic fluxes are produced by a main field winding 24 consisting of 156 winding turns of a number sixteen gauge wire conductor having approximately one ohm resistance and a reverse field winding 26 consisting of 390 winding turns of a number twenty-six gauge wire conductor having a resistance of approximately fifteen ohms.

The output of the three-phase output winding 22 is rectifier circuit generally designated by the reference numeral 90. The power rectifier circuit 90 includes six silicon diodes connected in a conventional three-phase full-wave rectifier bridge arrangement with the upper three diodes 92 providing positive voltage at junction 94. Junction 94 forms the generator positive direct current power output terminal. The lower three diodes 96 are connected to a common junction 98 providing the negative output terminal which is connected to a common ground indicated at 102. The rectifier circuit 90 is located in a housing attached to the frame of generator 10.

A cable conductor 104 is connected to the positive output terminal 94 to supply a load circuit connected to the generator which is supplied at one desired regulated direct current voltage of, for example, 14 volts. The generator load circiuts which are connected to the cable 104 include various direct current loads including a storage battery 108 having a positive terminal 110 and grounded negative terminal 112. The grounded terminals 102 and 112 are connected to a conductive frame portion of a vehicle. The additional direct current loads are connected as is the battery 108, between cable conductor 104 and a common ground.

The transistor voltage regulating system 70 of this invention is connected to the generator output by a conductor 116 which is connected to conductor 104 at junction 118. The conductor 116 applies the positive generator output voltage to one end of a voltage sensing circuit 120 and also supplies current to field winding 24. System 70 is also connected to an auxiliary rectifier or diode trio circuit designated by the reference numeral 122 including three silicon diodes each designated 123. Each diode 123 is connected to a separate terminal of output winding 22. The auxiliary rectifier circuit provides a system turn-oil" 8 or disconnect feature to prevent current drain from the battery 108.

The auxiliary rectifier circuit 122 is connected to the terminals of three phase generator output winding 22 to form an auxiliary bridge arrangement that includes the negative diodes 96 of the power rectifier circuit 90. The auxiliary bridge circuit 122 provides a positive voltage on conductor 124, 125 and 126 relative to the system ground potential. A current path can be traced from one terminal of output winding 22, through the auxiliary rectifier circuit 122, through either of the conductors 124, 125 or 126 to a grounded conductor 130 that is grounded at junction 132. The path is completed through grounded terminal 102 of the power rectifier circuit 90 and a second terminal of winding 22.

The main field winding 24 is supplied current by the voltage of positive power terminal 94 through a circuit including conductor 116, a resistor 134, a first output transistor comprising NPN transistor and grounded conductor 130. Resistor 134 is connected between conductor 116 and the upper end of winding 24 at junction 142. The collector electrode of transistor 140 is connected to lower end of Winding 24 at junction 144 with its emitter electrode connected to grounded conductor 130. The transistor 140 operates as a switching element to control the amount of excitation current supplied to main field winding 24.

The transistor 140 is interconnected to an NPN tran sistor designated 148 in a conventional Darlington amplifier arrangement. The collector electrodes are coupled together and connected to junction 144 and the emitter electrode of transistor 148 is directly coupled to the base electrode of transistor 140. The Darlington amplifier provides improved switching operation including an increased amplification factor due to the compound effect of the two transistors. Operative biasing at the base electrode of transistor 148 also biases the base input circuit of transistor 140, as is well known, so that the two transistors are concurrently biased conductive and nonconductive.

When the transistors 140 and 148 are biased conductive, excitation current is supplied through the low impedance collector-emitter circuit of transistor 140. This current is supplied from the output terminals of rectifier circuit 90 by the voltage produced in output winding 22. The winding 24 is substantially deenergized when the transistors 140 and 148 are biased nonconductive.

A field discharge diode 150 is connected across both the resistor 134 and winding 24 to suppress inductive voltage surges. The diode 150, also referred to as a free wheeling diode, provides a circuit path for the inductive energy developed by the sudden drop in current through main field winding 24 when transistor 140 is biased nonconductive.

The reverse field winding 26 is energized by excitation current supplied by the voltage appearing between conductor 124 and ground. A field discharge or free wheeling diode 154 is connected across winding 26 to circulate the stored inductive energy that is developed when the reverse field winding current is switched off. A second output transistor comprising NPN transistor 156 is connected in series between reverse field winding 26 and grounded conductor 130. Transistor 156 operates as a switching element operating between conductive and nonconductive states to control the excitation supplied to the winding 26 by the voltage produced by output winding 22.

The collector and emitter electrodes of transistor 156 are serially connected with winding 26 and the conductor 130. The base electrode of transistor 156 is connected at junction through a base input resistor 162 to conductor 125 and also to the collector electrode of driver transistor 158. The collector-emitter circuit of transistor 158 is connected across the junction 1'60 and conductor 130. The voltage of junction 160 varies in response to the conductive and nonconductive states of transistor 158. When transistor 158 is in a nonconducting state, the voltage of junction 160 rises to a high value to bias the transistor 156 conductive. The high voltage is provided by the positive voltage output of auxiliary rectifier circuit 122. When the transistor 8 is in a conducting state, the voltage of junction 1 drops and the baseemitter circuit of transistor 156 is substantially short circuited to bias transistor 15'6 nonconductive.

Also, the transistor 156 is biased nonconductive when the generator system is off since no voltage is produced through auxiliary rectifier circuit 122 to bias transistor 156 conductive. This prevents current discharge from battery 108 through winding 26 and the base-emitter circuit of transistor 156 and ground when the generator system is shut down.

The voltage sensing circuit of the regulator, designated generally by the numeral 120, controls the switching operation of output transistor 140 and output transistor 156 and is now described. The voltage sensing circuit includes a voltage divider network 170, a voltage reference means 172 and a second driver transistor designated 174.

The voltage divider network 170 includes a turn-off transistor comprising NPN transistor 176 having a collector electrode connected to one end of fixed resistor 178 and its emitter electrode connected to variable resistor 180. The other end of resistor 178 provides one end of the voltage divider and is connected to the junction 142. The other end of the variable resistor 180 forms the other end of the voltage divider and is connected to the ground conductor so that the voltage divider network is connected across the generator output. The slider tap of variable resistor provides the voltage divider output between junction 182 and ground which is a function of the output voltage of the generator.

The base electrode of transistor 176 is connected through a base current limiting resistor 184 to the conductor 126. Transistor 176 is biased conductive by the positive voltage of conductor 126 and is biased nonconductive when the generator system is oh and no generator voltage is being produced. The transistor 176 blocks discharge current from battery 108 through the voltage divider 170 to ground when the system is 01f.

Resistor 134, noted hereinabove, is also referred to as a pickup resistor since it causes the generator output to be raised to compensate for the voltage drop due to the resistance of cable 104. Junction 118 is physically close to the generator output terminal 94 when the regulating system is mounted within or near the frame of generator 10. In some vehicles, the battery 108 is mounted at a suflicient distance from the generator so that the voltage provided at battery 108 is somewhat lower than that sensed by the regulator system. The voltage regulating system maintains the generator output voltage substantially constant but changes in generator loads causes variation of load current. There is, accordingly, some variation in the voltage drop through the conductor 104. To maintain the state of charge of the battery 108 constant, resistor 134 is provided to maintain a substantially constant charging voltage at terminal 110. Battery charging voltage is somewhat critical since improper charging can damage the battery or shorten its useful lifetime.

The resistor 134 is connected to the junction 142 which is connected both to one end of the voltage divider 170 and to the main field winding 24. At a fixed generator speed the required main field winding current correspondingly varies with change in the generator loads. The current through resistor 134 then varies as the load current varies through conductor 104. When the current, and therefore the voltage drop, of the conductor 104 increases, the main field excitation current increases to increase the voltage drop across resistor 134. This increased voltage drop of resistor 134 is effectively subtracted from the voltage being sensed by voltage divider 170 to increase the generator output voltage. Conversely, a drop of load ourrent correspondingly decreases the required field current so that the output voltage of the generator will be lowered because there is less voltage drop across resistor 134. If the compensation for cable voltage drop is not required it is understood that the resistor 134 can be omitted.

Referring now further to the voltage sensing circuit 120, the output of voltage divider 170 is provided at the junction 182 which is connected to the slider tap of the variable resistor 180. Junction 182 is also connected to one end of a filter capacitor 186 at junction 188 and the opposite end of the capacitor is connected to conductor 130. Junction 188 is also connected to one end of the voltage reference means 172 including a silicon diode 190 and Zener diode 192. The anode of diode 190 is connected to junctions 188 and 182 and the cathode is connected to the cathode of the Zener diode 192 having a predetermined reverse breakdown voltage. The Zener reverse breakdown voltage characteristic varies with changes in ambient temperature and to compensate for this variation the voltage characteristic of diode 190 is selected to vary inversely. Accordingly, a substantially constant breakdown voltage response is provided by the diode 190 and Zener diode 192.

The reverse breakdown voltage of Zener diode 192 is selected so that it conducts reverse current when the voltage divider output potential at junction 182 has a predetermined value. The reverse current path is provided from junction 188 to the base-emitter circuit of transistor 174. The position of the slider tap of variable resistor 180 is accordingly selected to provide this breakdown voltage in accordance with the desired generator output voltage applied across voltage divider 170. As the slider tap is adjusted downward to decrease the resistance of variable resistor 180, a larger output voltage will be required to reach the breakdown voltage. This will increase the desired regulated generator output voltage. If the slider tap is moved upward to increase the resistance of resistor 180 a lower generator output voltage will produce the breakdown voltage.

The base electrode of transistor 174 is connected to the other end of the voltage reference means 172 at the anode of Zener diode 192. The collector electrode of transistor 174 is connected through a resistor 196 to the conductor 126 and the emitter electrode is connected to the grounded conductor 130. Transistor 174 is biased conductive when Zener diode 192 of the voltage reference means 172 reaches its breakdown voltage and the potential at the base of transistor 174 rises. The positive voltage at junction 182 of the voltage divider circuit provides the forward base biasing voltage so that transistor 174 is biased conductive. Accordingly, the transistor provides a voltage responsive means that is biased conductive in response to the output voltage of the voltage divider 170 and the reverse breakdown voltage characteristic of Zener diode 192.

The collector electrode of transistor 174 is connected to the base electrode of transistor 1-48 by conductor 198. A bias resistor 200 is connected between the conductor 198 and grounded conductor 130 to provide suitable input biasing resistance for transistor 148 and the Darlington amplifier circuit also including transistor 140. The junction 202 of conductor 198 is connected to the base electrode of transistor 158 through a base current limiting resistor 204. Transistor 174 is referred to as a driver transistor since it controls the voltage of conductor 19% to simultaneously control the voltage applied to the base circuits of transistors 148 and 158.

The voltage occurring at the collector electrode of transistor 174 is supplied by the voltage of conductor 126 and accordingly rises to a positive value when tran sistor 174 is nonconductive. The positive base voltages of transistors 148 and 158 forward bias the base-emitter circuits of transistors 148 and 140 and the base-emitter circuit of transistor 158. Base drive current flows through both base-emitter circuits of transistors 148 and 140 in accordance with the operation of a Darlington amplifier circuit so that both transistors 148 and 140 are biased conductive. Base drive current also flows through the base-emitter circuit of transistor 158 to bias the collector-emitter circuit conductive. Accordingly, the voltage of junction 1'60 drops to a low value to bias transistor 156 nonconductive.

When the transistor 174 is biased conductive, the voltage on conductor 198 drops to a low value corresponding to the ground potential of conductor 130 so that the base electrodes of transistors 148 and 158 are placed close to ground potential. The transistors 140 and 158 are biased nonconductive and the voltage of junction 160 at the base electrode of transistor 156 rises so that transistor 156 is biased conductive.

The operation of the generator voltage regulating system will now be described by reference to FIG. 4. Before the system is energized by driving the generator rotor, battery current is blocked by the diodes 92 of the rectifier circuit 90 and the nonconductive transistors of the voltage regulating system 70. Current drain from battery terminal 110 is accordingly prevented since no low impedance path exists to a grounded terminal. The generator will begin to develop a voltage in output winding 22 due to the permanent magnetic field when the rotor is driven by a vehicle engine. During generator operation, the output voltage is dependent upon the rotor speed, the amount of current supplied to the main field winding 24, and the flux produced by the permanent magnets 52 and 54 as described above.

The three phase voltage of output winding 22 is rectified by the power rectifier circuit 90 and auxiliary rectifier circuit 122. Positive direct current voltage appears between cable conductor 104 and ground and also between conductors 124, 125 and 126 and ground. Transistor 176 is biased conductive by the forward base biasing voltage of conductor 126 applied through the resistor 184. Accordingly, the voltage divider network 170 is connected across the generator output terminals of rectifier circuit 90 at junction 118. Also, the positive voltage of conductor 126 provides the forward biasing potential on conductor 198 to bias transistors 148 and 140 conductive and also to bias transistor 158 conductive. The transistor 156 is biased nonconductive and all the transistors of the regulating system are in a conductive state to increase the generator output voltage.

Current begins to flow through the resistor 134, main field winding 24 and transistor 140 as the generator output voltage begins to build up. The generator output voltage provides the current through main field winding 24 to produce the main field flux 74 which increases the output voltage of the generator. Since transistor 156 is biased nonconductive the reverse field Winding 26 is deenergized so that no reverse field flux 76 is produced.

The desired regulated output voltage is reached when the voltage across the voltage divider network 170 produces a voltage across the variable resistor 180 that is sufficient to reach the reverse breakdown voltage of Zener diode 192. When this happens, the base-emitter circuit of transistor 174 is forward biased to become conductive in its collector-emitter circuit and reduce the voltage at conductor 198 to a point where transistors 148 and 140 are biased nonconductive and also to bias transistor 158 nonconductive.

The main field winding excitation current is interrupted so that no main fieldfiux 74 is produced in Winding 24. The potential of junction 160 rises because it is effectively isolated from ground by the high impedance provided by the collector-emitter circuit of nonconductive transisfor 158.

Accordingly, the transistor 156 is biased conductive and the reverse field winding 26 is connected between the positive voltage of conductor 124 and ground so that reverse field excitation current fiows to produce the reverse field flux 76. The reverse field fiux 76 neutralizes the effect of the permanent magnet fluxes 78 and 80 produced by permanent magnets 52 and 54 to reduce the voltage producing effect of the generator magnetic circuit as explained hereinabove.

The generator output voltage, which is applied across the voltage divider network 170, accordingly decreases to the desired regulated voltage. The voltage divider output at junction 182 drops below the reverse breakdown voltage of Zener diode 192 so that the diode becomes nonconductive. The forward base biasing voltage of transistor 174 is blocked by Zener diode 192 and transistor 174 becomes nonconductive. The potential of conductor 198 rises due to the voltage of conductor 126 which is applied to the collector electrode of transistor 174. The base elec trodes of transistors 148 and become forward biased and the transistors are returned to a conductive condi tion. The main field winding 24 is again connected through the collector-emitter circuit of transistor 140 to the generator output voltage.

The potential of conductor 198 is coupled through junction 202 to provide the forward base biasing voltage of transistor 158 so that the collector-emitter circuit of tran sistor 158 is conductive. Since the potential at the junction 160 drops below the forward base biasing voltage of transistor 156, the transistor again becomes nonconductive and disconnects the reverse field winding 26 from the voltage supplied by conductor 124. Accordingly, only the main field flux 74 and permanent magnet fluxes 78 and 80 are being produced to generate an increasing voltage in the output winding 22.

The main and reverse field windings 24 and 2 6 are alternately excited at a high rate in accordance with the generator output voltage and the operation described above. The transistors 140 and 156 alternately conduct to respectively produce main and reverse flux fields in re sponse to the desired regulated output voltage.

Although one type of permanent magnet generator has been disclosed, it is contemplated that there are other generators using permanent magnets or having a residual magnetic flux produced by a magnetized portion of a generator magnetic circuit. These generators may incor porate a reverse field winding which opposes the effect of increasing the generator output voltage by a magnetic flux field which remains after the main field is deenergized. Accordingly, the main and reverse field windings would be energized cyclically by a voltage regulating system comprising the present invention.

While the. embodiments of the present invention as herein disclosed constitute a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A regulating system for an alternating current generator including, an output winding, a main field winding, a permanent magnet magnetic field and a reverse field winding for opposing the voltage producing effect of said permanent magnet field, said regulating system comprising: rectifier means having alternating current input terminals, connected to said output winding and direct current output terminals, first and second output transistors, means connecting the collector-emitter circuit of said first output transistor and said main field winding in a series connection and with said output winding, means connecting said reverse field winding in series with said output winding and the collector-emitter circuit of said second output transistor, a voltage sensing circuit connected to said direct current output terminals of said rectifier means, means connecting said voltage sensing circuit to the base of said first output transistor, means connecting said voltage sensing circuit to the base of said second output transisfor, said voltage sensing circuit developing a first voltage which is operative to bias said first output transistor conductive and bias said second output transistor nonconduc tive when the voltage of said direct current output termi nals is below a desired value and developing a second voltage which is operative to bias said first output transis for nonconductive and bias said second output transistor conductive when the voltage of said direct current output terminals is above the desired value, said second output transistor being biased nonconductive when said first output transistor is biased conductive to increase the generator output voltage, and said first output transistor being biased nonconducive when said second output transistor is biased conductive to energize said reverse field winding and produce a magnetic field in an opposing relationship to said permanent magnet field so that the generator output voltage is decreased.

2. A regulating system for an alternating current generator having a main field winding, a reverse field winding and an output winding, said regulating system comprising; first rectifier means connected with said output winding having direct current load terminals adapted to be connected with a direct current load circuit, second rectifier means connected with said output winding having an output connected to said reverse field winding, first and second output transistors, means connecting said main field winding and the collector-emitter circuit of said first output transistor in series and across the direct current load terminals of said first rectifier means, means connecting said reverse field winding and the output of said second rectifier means in a series connection including the collector-emitter circuit of said second output transistor, a voltage sensing means connected across said direct current load terminals, said voltage sensing means including means for producing a voltage which changes when the voltage across said direct current load terminals is above or below a desired regulated value, means coupling the base of said first output transistor with said voltage sensing means, said first output transistor being biased nonconductive when said voltage across the direct current load terminals is above said desired regulated value and being biased conductive when said voltage is below the desired regulated value, means coupling the base of said second output transistor to said voltage sensing means, said second output transistor being biased conductive when said voltage across the load terminals is above the desired regulated value and being biased nonconductive when the voltage is below the desired regulated value, whereby said first and second output transistors are biased alternately conductive and nonconductive in response to the voltage across said direct current load terminals.

3. A regulating system for a generator comprising; an alternating current generator having an output winding, a main field winding for causing a voltage to be induced in said output winding when said main field winding is supplied with current, said generator having a magnetic circuit including a magnetized portion producing a flux field to increase the voltage produced in said output winding, and a reverse field winding for producing a magnetic field in opposing relationship to the flux fields produced by said main field and said magnetized portion, a power rectifier circuit connected to said output winding and having positive and negative direct current output ter minals, a voltage sensing circuit including a voltage divider and a voltage reference means, said voltage sensing circuit being connected across said direct current output terminals and producing a voltage in response to a predetermined voltage occurring across said output terminals, a first output transistor having emitter, collector and base electrodes, means connecting the voltage sens- -ing circuit to said base electrode of said first output transistor, said voltage sensing circuit biasing said first output transistor conductive when the voltage across said direct current output terminals is below the predetermined voltage and biasing said first output transistor nonconductive when the voltage across the output terminals is above said predetermined voltage, means connecting said main field winding in series with said output winding and the collector and emitter electrodes of said first output transistor, a second output transistor having emitter, collector and base electrodes, means connecting said reverse field winding in series with said output winding and the collector and emitter electrodes of said second output transistor, a driver transistor having emitter, collector and base electrodes, means connecting the collector and emitter electrodes of said driver transistor to a base biasing circuit including the base electrode of said second output transistor, said second output transistor being biased conductive when said driver transistor is biased nonconductive and said second output transistor being biased nonconductive when said driver transistor is biased conductive, means connecting the base electrode of said driver transistor to said voltage sensing circuit, said voltage sensing circuit biasing said driver transistor conductive when the voltage across said direct current load terminals is below the predetermined voltage and biasing said driver transistor nonconductive when the voltage of said direct current load terminals is above the predetermined voltage, whereby said main field winding is energized when said first output transistor is conductive to increase the voltage of said output winding and said reverse field winding is energized when said second output transistor is conductive to oppose the magnetic flux of said magnetized portion thereby decreasing the output winding voltage.

4. A regulating system for a generator comprising; an alternating current generator having an output winding, a main field winding for developing a magnetic flux to produce voltage in said output winding, a plurality of permanent magnets providing a flux field to produce a voltage in said output winding in aiding relationship with the voltage produced by said main field winding flux, and reverse field winding for producing a magnetic flux which opposes the magnetic flux provided by said permanent magnets, a power rectifier circuit connected to said output winding and having a positive voltage terminal and a negative terminal, an auxiliary rectifier circuit connected to said output winding and having a positive voltage output relative to said negative terminal, a voltage sensing circuit including a voltage divider and a voltage responsive means, said voltage divider connected across said power rectifier circuit terminals and said voltage responsive means connected across said auxiliary rectifier output and said negative terminal, means for controlling said voltage responsive means connected between the output of said voltage divider and said voltage responsive means whereby said voltage responsive means develops a first voltage when the voltage across the terminals of said power rectifier is below a desired regulated value and develops a second voltage when the voltage across said power rectifier circuit terminals is above the desired regulated value, a first output transistor, the collectoremitter circuit of said first output transistor connected in series with said main field winding and said terminals of the power rectifier circuit, the base-emitter circuit of said first output transistor connected to said voltage responsive means, a second output transistor, the collectoremitter circuit of said second output transistor connected in series with said reverse field winding and the output of said auxiliary rectifier circuit, means including a resistor connecting the base-emitter circuit of said Second output transistor with said output of the auxiliary rectifier circuit, a driver transistor, the collector-emitter circuit of said driver transistor connected across said base-emitter circuit of said second output transistor, said second output transistor biased nonconductive when said driver transistor is conductive and biased conductive when said driver transistor is nonconductive, means including a resistor connecting the base-emitter circuit of said driver transistor to said voltage responsive means, said first output transistor and said driver transistor being biased conductive by said first voltage developed by said voltage responsive means and said first output transistor and said driver transistor being biased nonconductive by said second voltage developed by said voltage responsive means, whereby said main field and said reverse field windings are alternately energized so that when said main field winding is energized the voltage of said output winding is increased and when said reverse-field windingis energized to produce magnetic flux to oppose the magnetic flux of said permanent magnets the voltage of said output winding is decreased.

References Cited UNITED STATES PATENTS 3,017,562 1/1962 Duane 322-46 16 3,343,059 9/1967 Kirk et a1. 322-63 X 3,392,294 7/1968 Campbell 310-263 X BENJAMIN DOBECK, Primary Examiner 5 H. HUBERFELD, Assistant Examiner U.S. C1. X.R. 

